As energy costs are continuously rising and environmental protection is paid more attention, demands for energy conservation in a data center are becoming stronger. Under the premise of ensuring the safety and the high-performance operation of Information Technology (IT) equipments in the machine room of the data center, energy efficiency of the data center is improved and Power Usage Effectiveness (PUE) is reduced by comprehensively using various energy conservation approaches. Energy conservation and emission reduction has become one of purposes pursued by infrastructures in the data center.
In the conventional data center, a refrigerating unit provides chilled water to the end of an air conditioner to keep the IT equipments cooling down. The ratio of energy consumption of the refrigerating unit to energy consumption of the data center is about 40%. As a result, the energy consumption of the refrigerating unit is serious. Since the natural cooling (also called free cooling) system does not need the refrigerating unit to provide the cold source, energy consumption of the air conditioning system of the data center is significantly reduced, resulting in a remarkable energy conservation effect.
The common natural cooling systems include two types: the waterside natural cooling system and the air side natural cooling system. The water side natural cooling system is mainly to add a heat exchanger in addition to the original refrigerating unit. When a temperature of the outdoor environment is low, since the heat exchanger bypasses the refrigerating unit, outdoor cooling water is directly used to cool an indoor server. Although the water side natural cooling system is maturely and widely used, it occupies a large area and requires a number of heat exchanging operations. Accordingly, the energy conservation potential of the waterside natural cooling system is limited. The air side natural cooling system is to directly or indirectly cool the indoor server using outdoor cold air. Accordingly, the air side direct natural cooling system has a high heat exchanging efficiency and a large energy conservation potential. However, since there are risk factors such as outdoor environmental pollution and humidity, the reliability of the air side natural cooling system is risky. An optimization scheme is to indirectly exchange heat through an air-air heat exchanger to avoid this problem. However, the heat exchanger has a large size, a high cost, and a low heat exchanging efficiency.
The existing air side energy conservation natural cooling scheme for the data center generally adopts a special air conditioning unit with fresh air functions such as a direct fresh air unit or an indirect fresh air unit. However, the air conditioning unit is not adapted to the machine room building well, and requires the machine room to reserve a large amount of space for placement, air passage, or a maintenance area. Meanwhile, the existing air side energy conservation units need to be provided with a multi-layer filter screen to remove the pollution of the outdoor environment. However, the filter screen generates a large airflow resistance, which increases power consumption of a circulating fan and weakens the energy conservation effect. Moreover, the filter screen needs to be frequently replaced and maintained, which increases the operating complexity and cost. In addition, the existing natural cooling units are generally equipped with a compact multi-row heat exchanger to achieve requirements of heat exchange and humidity control. However, the heat exchanger may cause an adverse influence on the air resistance of the system, and simultaneously weaken the energy conservation effect.